The art of bagel preparation is ancient, as is the preparation of bread more broadly. The staling of bread has long been a problem, but it was not until the mid nineteenth century that it was clearly established that staling was not caused exclusively by moisture loss. In 1852, Boussingault reported that bread staled despite being sealed in a glass tube to prevent moisture loss. Staling has more recently been related to starch retrogradation, but this is also not the complete answer because crumb firmness is related to moisture content. Staling of bread is manifested in textural, visual and flavor changes--the net result is a strong negative correlation between staling and consumer acceptance.
There are many complex factors which impact on staling of bagels. The main ingredients include flour, water, yeast, sugar, and salt, in reasonable proportions to provide complete hydration with good forming and baking qualities. The intimate interaction of these dough components is affected by the mechanical action of mixing and the subsequent thermal effects of the production process. Other factors, not necessarily related to production, such as product storage temperature, moisture level, and packaging are interrelated and affect product freshness.
Irwin Stone, in U. S. Pat. No. 2,615,810, estimated that, in normal times, the annual wastage of stale bakery products accounted for from about 3.0 to about 4.7% of total wheat production. He postulated that the staling process could be divided into two parts: the crust which became soft and leathery due to the transfer of moisture from the crumb, and the crumb which becomes harder, tougher, more crumbly, and increasingly more opaque. He viewed the problem of crumb staling to be the most significant, and to alleviate it he taught the inclusion of a bacterial, starch-liquefying enzyme, such as .alpha.-amylase from B. mesentericus or B. subtilis, in the dough.
However, as reported by Olesen in WO 91/04669, the use of .alpha.-amylase for retarding staling has not become widespread--assumedly because the products of the hydrolysis are malto dextrins (with 20-100 glucose units in the molecule). These malto dextrins have a sticky consistency in themselves and are believed to result in the formation of a sticky or gummy crumb when used in excess. Olesen also reported that alleviation of the asserted adverse effects of .alpha.-amylase was addressed in U.S. Pat. No. 4,654,216 which suggested using pullanase (a debranching enzyme) in combination with the .alpha.-amylase. He further reported that monoglycerides have been suggested as antistaling ingredients which may be able to penetrate the amylose helical structure to retard retrogradation.
Given the review of antistaling technology prior to his efforts, however, Olesen presents what he asserts is a different approach--the use of an enzyme which is capable of retarding staling but does not result in the production of branched dextrins. The enzymes identified are exoamylases, such as .alpha.-amylases derived from various Bacillus strains. In his process, the enzyme is added to the dough in liquid form to a simple white pan bread formulation. The effectiveness of enzymes of this type is confirmed by a report issued by the American Baker's Institute entitled "Novamyl.RTM. as a Crumb Softener for Bagels". However, the preparation of a bagel of high initial quality which is also shelf-stable in terms of microbiological stability and the texture of the crumb and the crust, as well as the textural contrast between them, has not been made available to the art.
There remains a need for a process to prepare bagels with an improved combination of quality and shelf stability.